1. Field of the Invention
The present invention relates to an assist assembly for propulsion of a tip device of an endoscope into a body.
2. Description Related to the Prior Art
In medical and industrial fields, an endoscope is widely used for imaging of a body. The endoscope has a handle and an elongated tube for entry in the body. A tip device of the elongated tube contains an imaging unit such as a CCD. An image created by the imaging unit is displayed on a monitor.
Various forms of assist assembly for the endoscope have been suggested for assisting the entry of the endoscope in view of difficulty in the entry of the endoscope. For example, U.S. Ser. No. 2005/272,976 (corresponding to JP-A2005-253892) discloses the assist assembly for the endoscope (referred to as a propulsion device for an endoscope according to the publication) including a tubular support and a circulation device (endless track device), the support being mounted on the tip device of the elongated tube of the endoscope, the circulation device being secured to the support movably in circulation. The circulation device mentioned above moves endlessly in a state of contact of its outer surface with a tissue wall of the body, for example, a gastrointestinal tract of a human body, and thus applies force of propulsion to the tip device. Accordingly, it is possible easily to enter the endoscope even in the gastrointestinal tract of a very tortuous form, for example, a large intestine.
In the assist assembly for the endoscope mentioned above, a motor rotates a wire. A magnetic bar secured to an end of the wire is rotated to move the circulation device in circulation, the circulation device being extended in contact with magnetic rollers. The magnetic bar is in a form in which N and S poles are wound alternately and helically, and operates as a worm gear. Also, the rollers have N and S poles arranged alternately on its outer surface, and operate as worm wheels. The circulation device moves in the circulation in a state of contact with the tissue wall of the gastrointestinal tract, and constantly receives pressure from the tissue wall. The circulation device is likely to offset on the rollers. Upon occurrence of the offset, the circulation device may slip to drop driving force of the circulation device, which may become unable to assist the entry of the endoscope.